Optical networks and the like (e.g., Dense Wavelength Division Multiplexed (DWDM), Optical Transport Network (OTN), and the like) at various layers are deploying control plane systems and methods. Control planes provide automatic allocation and management of network resources in an end-to-end manner, including managing protection such as through mesh restoration. Example control planes may include Automatically Switched Optical Network (ASON) as defined in ITU-T G.8080/Y.1304, Architecture for the automatically switched optical network (ASON) (02/2005), the contents of which are incorporated herein by reference; Generalized Multi-Protocol Label Switching (GMPLS) Architecture as defined in IETF Request for Comments (RFC): 3945 (10/2004) and the like, the contents of which are incorporated herein by reference; Optical Signaling and Routing Protocol (OSRP) from Ciena Corporation which is an optical signaling and routing protocol similar to PNNI (Private Network-to-Network Interface) and MPLS; or any other type control plane for controlling network elements at multiple layers, and establishing connections therebetween. Control planes are configured to establish end-to-end signaled connections such as Subnetwork Connections (SNCs) in ASON or OSRP, and Label Switched Paths (LSPs) in GMPLS and MPLS. Control planes are configured to compute paths, to route/signal the SNCs/LSPs, and program the underlying hardware accordingly. As described herein, such optical networks provide Layer 1 connectivity including providing protection at Layer 1.
Layer 2 packet traffic operates over the optical network. Layer 2 networks can also support protection, such as via G.8031/Y.1342 (01/15) “Ethernet linear protection switching” and G.8032/Y.1344 (08/15) “Ethernet ring protection switching,” the contents of each are incorporated herein by reference. When there is a fault affecting the optical network at Layer 1, there is a need to avoid problems between the protection switching techniques at Layer 1 and Layer 2. Specifically, the objective is to avoid sympathetic switches at Layer 2 during any Layer 1 protection switch or maintenance activity.
There are generally two conventional approaches to avoid a Layer 2 sympathetic switch. First, a hold-off timer can be used to delay the Layer 1 defect propagation to the Layer 2 network, such that a Layer 2 port is notified of Layer 1 failures only after expiration of the hold-off timer. Second, Continuity Check Message (CCM) timeout can be set such that the time is greater than a mesh restoration time in the Layer 1 network (e.g., typically around 300 ms). Note, the Layer 2 network utilizes CCMs to determine faults. Of course, configuring the CCM timeout greater than the mesh restoration significantly delays failure detection for Ethernet-only segments. Also, if there is no protection or if mesh restoration is unavailable, the Layer 2 protection will only operate after the hold-off timer or the greater CCM timeout. Further, Layer 1 protection times vary significantly based on the underlying protection mechanisms, e.g., mesh restoration (˜300 ms) versus Automatic Protection Switching (APS) (<50 ms).
Thus, the conventional approaches delay the propagation of Layer 1 faults such that Layer 2 is not made aware of Layer 1 faults for the delay duration. Also, this makes the Layer 1 switching a priority which may not be possible in all scenarios. That is, the available bandwidth can change in the Layer 1 network and protection for Layer 1 paths is not always guaranteed. The conventional approaches assume there is always Layer 1 protection available.